This invention relates to a radioactive isotope source, and more particularly to an encapsulated radioactive isotope source which is designed to permit re-encapsulation and reuse of the radioactive isotope.
Various types of analytical instruments use a radioactive isotope source in order to obtain measurements of the physical characteristics or properties of a test specimen. For example, there are commercially available instruments which use a radioactive isotope source for measuring properties such as density, composition, moisture content, thickness, etc. Examples of such test instruments are described in the following United States patents owned by applicants' assignee: U.S. Pat. Nos. 4,525,854; 4,542,472; 4,587,623; 4,766,319; 4,874,950; 4,979,197; and 5,155,356.
In nuclear instruments of the general type illustrated by the above patents, the radioactive isotopes are typically contained in a capsule. For example, where the isotopes are americium and beryllium, small pellets of the americium and beryllium are packaged in a stainless steel capsule.
Even though the radioactive half-life of these isotopes is very long (e.g. over 400 years) it is often recommended that the instruments be returned to the manufacturer periodically so that the radioactive isotope source can be reconditioned or replaced. This is because the weld in the stainless steel capsule may lose strength or become brittle after a number of years.
In the past, used radioactive isotope source capsules were collected and sent to a disposal site for radioactive materials. However, it has become increasingly difficult to find disposal sites which will accept such radioactive materials.